Antenna matching system

Abstract

A system for adjusting the antenna matching network of a radio system in the presence of an interfering signal in the matching network being adjusted comprises a loop from which the interfering signal is cancelled by an adaptive interference cancellation (AIC) system. The AIC system receives an interference sensor signal having the frequency of the interfering signal. Means responsive to the interference sensor signal and phase and amplitude control signals provides a modified interference sensor signal having a phase and amplitude determined by the control signals. This modified interference sensor signal is combined with a mismatch signal which is derived from the signal in the matching network to produce a modified mismatch signal. An adaptive interference cancellation processor is responsive to the modified mismatch signal for providing the phase and amplitude control signals of values to reduce the amplitude of the interfering signal frequency in the modified mismatch signal relative to its amplitude in the mismatch signal. An adjustment processor responds to the modified mismatch signal to control an impedance adjuster for adjusting the impedance of the matching network.

What is claimed is: 
     
       1. In a system for adjusting the impedance of an antenna matching network to match an antenna at a desired carrier frequency in which said system is of the type including said antenna matching network, means for adjusting the impedance of said matching network, means for providing a mismatch signal representative of the condition of said matching network during the transmission of a tuning signal therethrough and a matching adjustment processor responsive to said mismatch signal for controlling said means for adjusting, the improvement for cancelling from said mismatch signal an interfering signal having a different frequency than said tuning signal, comprising: means for providing an interference sensor signal having the frequency of said interfering signal;   means responsive to said interference sensor signal and phase and amplitude control signals for providing a modified interference sensor signal having a phase and amplitude determined by said control signals;   means for combining said modified interference sensor signal and said mismatch signal to provide a modified mismatch signal;   an adaptive interference cancellation (AIC) processing system responsive to said modified mismatch signal for providing said phase and amplitude control signals of values that reduce the amplitude of said interfering signal in said modified mismatch signal relative to its amplitude in said mismatch signal; and   means for coupling said modified mismatch signal to said adjustment processor.   
     
     
       2. The improvement recited in claim 1 wherein said AIC processing system comprises: means for measuring the amplitude of said interfering signal in said modified mismatch signal; and   means for adaptive interference cancellation (AIC) responsive to said amplitude measurement for providing said control signals.   
     
     
       3. The improvement recited in claim 2 wherein said means for adaptive interference cancellation includes: means for selecting initial values for said control signals;   means for storing said measured amplitude of the resulting modified mismatch signal; and   means for updating said control signals to minimize said measured amplitude of said modified mismatch signal.   
     
     
       4. The improvement recited in claim 3 wherein said means for updating said control signals comprises: means for selecting current control signal values by modifying a previous set of control signal values;   means for storing said current control signal values,   means for storing the current measured amplitude of the modified mismatch signal which results from said current control signals;   means for comparing said current stored measurement of said modified mismatch signal with other stored measurements of said modified mismatch signal; and   means for selecting, in accordance with the results of said comparisons, an updated set of control signal values to replace said previous set of control signal values.   
     
     
       5. In a system for adjusting the impedance of an antenna matching network to match an antenna at a desired carrier frequency in which said system is of the type having a first loop including said antenna matching network, means for adjusting the impedance of said matching network, means for providing a mismatch signal representative of the condition of said matching network during the transmission of a tuning signal therethrough and a matching adjustment processor responsive to said mismatch signal for controlling said means for adjusting, the improvement comprising: a second loop for cancelling from said mismatch signal an interfering signal having a different frequency than said tuning signal, said second loop comprising: means for providing an interference sensor signal having the frequency of said interfering signal;   means responsive to said interference sensor signal and phase and amplitude control signals for providing a modified interference sensor signal having a phase and an amplitude determined by said control signals;   means for combining said modified interference sensor signal and said mismatch signal to provide a modified mismatch signal; and   an adaptive interference cancellation (AIC) processing system responsive to said modified mismatch signal for providing phase and amplitude control signals of values that reduce the amplitude of said interfering signal in said modified mismatch signal relative to its amplitude in said mismatch signal; and     means for selectively switching said second loop into and out of said first loop and for coupling said modified mismatch signal to said adjustment processor in place of said mismatch signal when said second loop is switched into said first loop.   
     
     
       6. In a system for adjusting the impedance of an antenna matching network to match an antenna at a desired carrier frequency in which said system is of the type including said antenna matching network, means for adjusting the impedance of said matching network, means for providing a mismatch signal representative of the condition of said matching network during the transmission of a tuning signal therethrough, a matching adjustment processor responsive to said mismatch signal for controlling said means for adjusting, means for receiving an interference sensor signal having the frequency of an interfering signal, modifier means responsive to said interference sensor signal and phase and amplitude control signals for providing a modified interference sensor signal having a phase and amplitude determined by said control signals, means for combining said modified interference sensor signal and said mismatch signal to provide a modified mismatch signal, an adaptive interference cancellation processing system responsive to said modified mismatch signal for providing said phase and amplitude control signals of values that reduce the amplitude of said interfering signal in said modified mismatch signal relative to its amplitude in said mismatch signal, and means for coupling said modified mismatch signal to said adjustment processor, a method of cancelling interference from said mismatch signal comprising the steps of: (a) providing from said AIC processor to said modifier means amplitude and phase control signals to cause the modified interference sensor signal to have a zero amplitude;   (b) measuring the amplitude of said interfering signal in said modified mismatch signal while said modified interference sensor signal amplitude is zero;   (c) establishing an amplitude control signal which will set the amplitude of said modified interference sensor signal to substanitally the amplitude measured in step (b) and providing said established amplitude control signal from said AIC processor to said modifier means;   (d) providng from said AIC processor to said modifier means a plurality of phase control signal values and measuring the resulting amplitude of said interfering signal in said modified mismatch signal for each of said phase control signal values; and   (e) selecting as a new phase control signal value the one of said plurality of phase control signal values which in step (d) results in a minimum measured amplitude of said interfering signal in said modified mismatch signal.   
     
     
       7. The method recited in claim 6 further comprising the steps of: (f) providing from said AIC processor to said modifier means an amplitude control signal having a value to provide said modified interference sensor signal with an amplitude equal to its established value plus the minimum measured amplitude of said interfering signal in step (e) and measuring the resulting amplitude of said interfering signal in said modified mismatch signal;   (g) providing from said AIC processor to said modifier means an amplitude control signal having a value to provide said modified interference sensor signal with an amplitude equal to said established value minus the minimum measured amplitude of said interfering signal measured in step (e) and measuring the resulting amplitude of said interfering signal in said modified mismatch signal; and   (h) selecting as a new established amplitude control signal value the value in step (f) or step (g), whichever resulted in the smaller measured interfering signal in said modified mismatch signal and returning to step (d).